Polymers are widely used as protective, dielectric, passivation and redistribution layers in microelectronic devices and microelectronic device packaging, microelectromechanical systems (MEMS) and in optoelectronic devices. In particular, norbornene-type polymers have been found to be valuable for such uses. For example, films formed from such polymers have found use in thin-film transistor type liquid crystal displays (TFT LCD) and organic electro-luminescence (OEL) devices to insulate the elements or wiring and/or to planarize device surfaces, and in some cases serve to form projections over a display electrode surface for orientation control of liquid crystal molecules in LCD devices or as spacers between electrodes in OEL and LCD devices. Further, films formed from such polymers are also useful in mounting semiconductor devices on printed wiring boards or other mounting substrates where such films serve to insulate between the semiconductor device and the circuitry of such board or substrate as well as serving to attach such devices to such board or substrate.
To be effective in the aforementioned exemplary uses, the films or structures formed must be able to withstand subsequent processing while maintaining their desirable properties during the useful life of device within which they are incorporated. Where such materials are used in optical applications such as displays and/or optical semiconductor devices, the materials must also form films that are highly transparent at appropriate wavelengths of light.
While in the past various materials have been found useful for some of the applications described above, the higher integration and/or miniaturization of displays, semiconductor devices and printed wiring boards has shown that the continued use of such previously known materials is problematic and/or limited. For example, while currently known polyimide resins generally have adequate high temperature performance, they do not have a low enough permittivity to be effective in highly integrated and/or miniaturized devices having increased wiring density and high signal speed. In addition, polyimide resins are generally not transparent enough for many optical applications. One such known polyimide material is the positive type photosensitive resin encompassing a polyimide precursor and a diazoquinone-type compound disclosed in Japanese Patent No. 3,262,108.
Other currently known materials, such as the acrylic resin based radiation-sensitive composition disclosed in Laid-open Japanese Patent Application No. Hei 5-165214 or the alicyclic olefin resin disclosed in Laid-open Japanese Patent Application No. 2003-162054 are also problematic or limiting in that while exhibiting adequate transparency, such resins do not have adequate heat resistance to withstand subsequent processing.
Recently U.S. Pat. No. 7,022,790 described a negative-tone norbornene-type polymer that can be provided as a self-imagable composition and which is the basis of a family of resin compositions (Avatrel® (Promerus LLC)). While this family of products has gained commercial success, due in significant part to its ability to form thick self-imagable films (≧30 μm), such success has been limited by its requirement for a solvent based image development process which differs from the more commonly employed aqueous base development process (employing 0.26N TMAH (tetramethylammonium hydroxide)) used for fabricating the aforementioned devices.
More recently, U.S. Pat. No. 7,524,594 ('594 patent), disclosed an aqueous base developable positive-tone Avatrel® resin composition ('594 resin) that has been shown to be appropriate for use in many of the aforementioned applications. However, the use of such '594 resin has proven to be limited to applications that only require the formation of relatively thin polymer films, for example films having a thickness of 20 microns (μm) or less, and where the aspect ratios obtained after imaging, do not exceed about 5 to 1.
Therefore it would be advantageous to have a resin composition that can be used for forming films having a thickness of 30 μm or greater where such films are highly transparent, have a low permittivity (less than or equal to that of thermal silicon oxide) and have high heat resistance (sufficient to withstand subsequent processing). Further, it would be advantageous if such a resin composition was self-imagable, that is to say that portions of films formed therefrom respond directly to an image-wise exposure to form a patterned film. Further still, it would be advantageous for such a self-imagable resin composition to employ an aqueous base developer, such as an aqueous alkali solution, for the development of the aforementioned pattern.